Fig. 1. Schematic diagram of the essential components of a ‘half-wavelength’ (acoustic pathlength in the aqueous phase) (a) and a “quarter-wavelength” (b) resonators showing the transducer, reflector and single nodal plane towards which particles that are (1) initially randomly distributed in suspension (2) move to and then (3) concentrate in that plane. Reproduced with permission from Kuznetsova and Coakley (2004).

Fig. 2. Types of acoustic streaming: container-scale Eckart streaming (a), Rayleigh counter-rotating vortices in λ/2 standing wave resonator (b), Schlichting streaming near the container boundary of Δ thickness (Spengler, 2002) (c) and near an oscillating cylinder (d); z is direction of sound propagation.

Fig. 3. (a) Simulation of acoustic pressure across a 0.135 mm fluid layer and 70 μm of the reflector for reflector thicknesses of 0.98, 1.00 and 1.02 mm; frequency f 2.82 MHz. (b) Capture of 1 μm particles (concentration 10⁷ particle/ml) for glass reflectors of different depths (dark grey points are simulated data, and light grey are experimental data). Each experimental point represents one slide (mean ± S.E.M.) from which 15 fields of view were counted (acoustic pressure P₀ 460 kPa, assay time 2 min, flow rate 0.2 ml/min). Reproduced with permission from Martin et al. (2005).

Fig. 4. Capture of 1 μm biotinylated particles for P₀ 460 kPa, assay time 2 min, flow rate 0.1 ml/min and slide thickness 1.01 mm with (diamond-shaped points) and without (squares) ultrasound. The slopes of the lines are 0.82 and 0.87 for sonicated and control samples, respectively. Each point is the mean for one slide from which 15 images were processed. Reproduced with permission from Martin et al. (2005).

Fig. 5. Schematic of the ultrasound-MCLW instrumental set-up: (1) sample volume of λ/4 acoustic pathlength depth; (2) microscope slide with a waveguide layer, which determines evanescent field in the adjacent volume of the sample; (3) piezoelectric transducer; (4) coupling steel layer; (5) red laser diode; (6) detector; (7) prism; (8) CCD camera.

Fig. 6. Mixing chamber (a) overview: the adhesive tape, with a thickness of 200 μm, serves as a spacing gasket to define the shape and dimension (16 mm × 16 mm) of the chamber; the cover slip has a number of air pockets (500 μm in depth and 500 μm in diameter) distributed uniformly above the chamber with a pitch of 2 mm; a 15 mm diameter piezoelectric (PZT) was bonded onto the external surface of the cover slip. (b) Side view (Liu et al., 2002). Reproduced with the permission of the publisher.

Fig. 7. Set-up for acceleration of DNA hybridization by cavitation micro-streaming (Liu et al., 2003). Reproduced with the permission of the publisher.

Fig. 8. Streaming pattern in the ultrasonic active area near the reflector visualised by 200 nm particles; 10× magnification. Rings indicate the centres of Rayleigh-type vortices, 1.75 MHz. Reproduced with permission from Kuznetsova et al. (2005).

Fig. 9. Particle capture for different suspension concentrations; each point is the mean for one glass from which 20 images (170 μm × 140 μm) were processed; the standard error of each capture mean is less than 10% of the mean. Reproduced with permission from Kuznetsova et al. (2005).